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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var num=10;
        console.log(typeof num);


        var arr=[10,20,30];
        //console.log(typeof arr); 不能判断

        console.log(Array.isArray(arr));
     
    </script>
</body>
</html>